This section provides background information related to the present disclosure which is not necessarily prior art.
Transmission clutches often find utility in vehicles where they modulate the amount of torque applied to transmission components by an engine. Automatic transmissions provide smooth shifting between gears. Planetary and dual-clutch transmissions are two different forms of automatic transmissions. Planetary automatic transmissions may have lower gear sliding-related losses relative to dual-clutch transmissions because planetary automatic transmissions typically have smaller gear modules (shorter gear teeth) than those used in dual-clutch transmissions. In addition, planetary automatic transmissions often utilize lower viscosity lubricant for gear and clutch protection in comparison to dual-clutch transmissions. Nonetheless, planetary automatic transmissions are usually less efficient than dual-clutch transmissions because planetary automatic transmissions utilize a larger number of wet clutches (i.e., friction-plate clutches) in comparison to dual-clutch transmissions, which typically have switch-type clutches such as dog clutches.
Clutch inefficiency in planetary automatic transmissions comes primarily from the drag-related losses associated with spinning the disengaged friction plates of the wet clutches. While drag-related losses can be minimized by providing adequate spacing between the friction plates, such additional spacing typically results in longer shift times and larger overall packaging dimensions.
A dog clutch or other switch-type clutch arrangement may provide a more efficient clutch configuration in its disengaged state. However, use of such switch-type clutches does not allow for appropriate gradual energy dissipation and torque transfer, thereby resulting in abrupt gear shifts. Thus, while wet clutches provide a longer shift time when compared to dog clutches or other switch-type clutch arrangements (and therefore smoother shifts), wet clutches suffer from the disadvantage of spinning losses when disengaged. What is needed is a clutch assembly that has improved efficiency over conventional wet clutch assemblies and reduced noise, vibration, and harshness (smoother shifts) in comparison to dog clutch or other switch-type clutch arrangements.